Polyimides (PI) are heterocyclic polymers commonly prepared by the condensation reaction of an aromatic diamine with an aromatic dianhydride or derivative thereof and having a repeat unit of the general structure ##STR1## where Ar is a tetravalent aromatic radical such as 1,2,4,5-tetrasubstituted benzene. Ar may also be a bis(o-diphenylene) having the general structure ##STR2## where Y=nil, O, S, SO.sub.2, CO, C(CH.sub.3).sub.2, or any other appropriate divalent radical. Ar' is a divalent aromatic radical which may be 1,3-phenylene, 1,4-phenylene, 4,4'-biphenylene, 4,4'-oxydiphenylene, 4,4'-sulfonyldiphenylene, or any other appropriate divalent radical.
The synthesis and characterization of PI has been extensively studied and documented. Reviews on PI are available. [J. W. Verbicky, Jr., "Polyimides" in Encyclopedia of Polymer Science and Engineering, 2.sup.nd Ed., John Wiley and Sons, New York, Vol. 12, 364 (1988); C. E. Sroog, Prog. Polym. Sci., 16, 591 (1991)].
A variety of monomers, oligomers and polymers containing ethynyl (acetylenic) and substituted ethynyl (i.e. phenylethynyl) groups have been reported. The ethynyl groups in the polymer are either pendant to the chain, in the chain, or at the chain ends. Many of these materials have been used to prepare coatings, moldings, adhesives and composites [P. M. Hergenrother, "Acetylene Terminated Prepolymers" in Encyclopedia of Polymer Science and Engineering, John Wiley and Sons, New York, Vol. 1, 61 (1985)]. Good processability by either solution casting and/or compression molding has been observed for the ethynyl and substituted ethynyl containing materials. In general, thermally cured ethynyl and substituted ethynyl containing materials exhibit a favorable combination of physical and mechanical properties. Some ethynyl endcapped materials such as the Thermid.RTM. resins are commercially available (National Starch and Chemical Co., Bridgewater, N.J. 08807). Phenylethynyl containing amines have been used to terminate imide oligomers [F. W. Harris, A. Pamidimuhkala, R. Gupta, S. Das, T. Wu, and G. Mock, Polym. Prep., 24 (2), 325, 1983; F. W. Harris, A. Pamidimuhkala, R. Gupta, S. Das, T. Wu, and G. Mock, J. Macromol. Sci.-Chem., A21 (8 & 9), 1117 (1984); C. W. Paul, R. A. Schultz, and S. P. Fenelli, "High-Temperature Curing Endcaps For Polyimide Oligomers" in Advances in Polyimide Science and Technology, (Ed. C. Feger, M. M. Khoyasteh, and M. S. Htoo), Technomic Publishing Co., Inc., Lancaster, Pa., 1993, p. 220; R. G. Byrant, B. J. Jensen, and P. M. Hergenrother, Polym. Prep., 34 (1), 566, 1993]. Imide oligomers terminated with ethynyl phthalic anhydride [P. M. Hergenrother, Polym. Prep., 21 (1), 81, 1980] and substituted ethynyl phthalic acid derivatives [S. Hino, S. Sato, K. Kora, and O. Suzuki, Jpn. Kokai Tokkyo Koho JP 63, 196, 564. Aug 15, 1988; Chem. Abstr., 115573w, 110, (1989)] have been reported.
It is a primary object of the present invention to provide novel phenylethynyl phthalic anhydrides and new imide oligomers endcapped with phenylethynyl groups, as well as polymers prepared therefrom which exhibit higher elongations, higher glass transition temperatures and higher fracture toughness, as compared to similar materials.
Another object of the present invention is to provide novel polymeric materials that are useful as adhesives, coatings, films, moldings and composite matrices.
Another object of the present invention is the composition of several new phenylethynyl phthalic anhydride (PEPA) endcapping reagents.